The present invention relates to a semiconductor integrated circuit device, and particularly to a semiconductor integrated circuit device incorporating a memory circuit and a microprocessor.
There is a semiconductor integrated circuit device incorporating memory circuits and a microprocessor (hereinafter referred to as a CPU). For example, there is a semiconductor integrated circuit device referred to as the so-called SoC (System on a Chip) obtained by forming memory circuits and a CPU in one semiconductor chip. Such a semiconductor integrated circuit device is used in many fields.
Recently, the market for electronic commerce services carried out over the Internet such as e-commerce and Internet banking has been steadily expanding. Further, electronic money services using IC cards are already in widespread use and are entering a period of expansion. Many semiconductor integrated circuit devices are also used in these electronic commerce services and electronic money services. Particularly in these services, money and/or personal information are dealt with; therefore, a higher level of security is always required. Accordingly, for semiconductor integrated circuit devices used in these services, a higher level of security is also required.
Security techniques include a software-level technique and a hardware-level technique. At the software level, for example by an encryption technique centered on a strong encryption algorithm, a higher level of security is going to be achieved. On the other hand, at the hardware level as well, attempts have been made to physically implement an encryption algorithm. However, there is pointed out a possibility of permitting an attacker such as the so-called hacker (cracker) to decrypt a secret key.
At the time of manufacturing a semiconductor integrated circuit device, an ID (Identification) is stored in a fuse or a nonvolatile memory circuit incorporated therein. In this case, there is pointed out a problem that there is a risk that data stored at the time of manufacture is falsified in actual use or a possibility that the semiconductor chip itself is cloned.
In order to solve such a problem, there is a proposal to generate an ID unique to a semiconductor integrated circuit device, focusing on variations occurring at the time of manufacturing the semiconductor integrated circuit device. For example, in a semiconductor chip where field-effect transistors (hereinafter referred to as MOSFETs) are formed as elements, there is a proposal to generate an ID (unique ID) unique to the semiconductor chip, using variations of MOSFETs occurring during manufacturing. In accordance with such a proposal, it is possible to generate a physically unclonable semiconductor chip unique ID (PUF: Physical Unclonable Function).